This invention relates to a process for cleaving aromatic steroid ethers.
The splitting of ethers of aromatic alcohls requires, as is known, more vigorous conditions and reagents than the splitting of purely aliphatic ethers. Frequently, alkyl ethers are utilized in steroid syntheses for the protection of hydroxy groups, because this grouping withstands almost all reactions. However, precisely because of this great resistance displayed by these ethers against reagents, difficulties are often encountered in the liberation of the hydroxy groups protected by such etherification after the synthesis, without affecting other groups of the molecule during this step. The aromatic steroid ethers are particularly resistant. They are split only under extreme reaction conditions, such as, for example, by treatment with strong acids, such as hydrogen bromide in glacial acetic acid (See German Unexamined Laid-Open Application DOS 1,924,222) or with a hydrochloric acid-pyridine complex at high temperatures. See J. Chem. Soc. (London), 1963, 5072; Ann. Chem. 705 (1967) 211. However, many steroid ethers are sensitive to acids, for example, those wherein acids can cause rearrangements or shifting of double bonds. The only known method for splitting of aromatic steroid ethers which is not conducted in an acidic medium employs Grignard reagents at temperatures of about 160.degree. C. See Tetrahedron 26 (1970) 1917.
Accordingly, it is an object of this invention to provide a process for splitting of ethers of aromatic steroid alcohols, particularly those with at least one additional double bond in the steroid molecule which can be conducted under non-acidic, gentle conditions, and thus which does not have the aforedescribed disadvantages. Other objects will be apparent to those skilled in the art.